In terrestrial digital television (DTV) applications, the received signal is not always direct. For example, the received DTV signal may be reflected by objects, geographic features (e.g., mountains), or may be affected by weather conditions. As a result, unlike cable TV signals, DTV signals are subject to large drops in the received signals, referred to as fading.
In addition, DTV low noise amplifiers typically have requirements that exceed the requirements of cable TV low noise amplifiers. For example, a DTV low noise amplifier typically requires more gain, a lower noise figure, and needs to handle relatively strong adjacent channels. Off-air DTV signals can vary widely in terms of received power level and can come in quite strongly. In some cases, the desired channel is very weak, and can have a very strong adjacent channel, for example, at a level of 40-50 dB stronger than the desired signal.
Accordingly, what is needed is an amplifier that can rapidly adapt to signals with large amounts of fading.
What is further needed is a system that can selectively respond faster or slower to a detected power level and achieve a linear type of response while still providing benefits of digital gain control for downstream power management.
The present invention will now be described with reference to the accompanying drawings. In the drawings, like reference numbers can indicate identical or functionally similar elements. Additionally, the left-most digit(s) of a reference number may identify the drawing in which the reference number first appears.